Received signal strength indicator (RSSI) is a measurement of a power present in a received signal of a communication receiver. In practice, the received signal is usually an AC (alternating current) signal. To detect the power present in an AC signal, a rectification circuit is needed. By rectification, an AC signal is converted into a DC (direct current) signal, whose power can be conveniently measured. In prior art, the rectification circuit is usually accomplished by using a diode circuit. However, a diode has an inherent non-zero threshold voltage (which is typically 0.6V) and therefore a diode circuit cannot rectify a small AC signal whose amplitude is below its threshold voltage.
What is disclosed is a method and apparatus for detecting a small received signal.